Integumentary System 343

8/11/2019 Integumentary System 343

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The Integumentary System


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General Anatomy

The largest organ;composed of 4 tissue

types18 square feet1-2 mm thick

Weight 10 lbs.

Skin and its accessory structuresstructurefunctiongrowth and repair

developmentagingdisorders


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Overview of Epidermis

Stratified squamousepithelium

Contains no blood vessels4 types of cells5 distinct strata (layers) of

cells


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Cell types of the Epidermis Keratinocytes--90% produce keratin

Melanocytes-----8 % produces melanin pigment melanin transferred to other cells

with long cell process

Langerhan cells from bone marrow provide immunity

Merkel cells in deepest layer form touch receptor with sensory

neuron


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Layers (Strata) of the Epidermis

Stratum corneumStratum lucidum

Stratum granulosumStratum spinosumStratum basale


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Stratum BasaleDeepest single layer of cellsCalled stratum germinativumCombination of merkel cells,

melanocytes, keratinocytes &stem cells that dividerepeatedly


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Stratum Spinosum

8 to 10 cell layers held togetherby desmosomes

During slide preparation, cellsshrink and look spinyMelanin taken in by phagocytosisfrom nearby melanocytes


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Stratum Granulosum

3 - 5 layers of flat dyingcells

Show nucleardegenerationContain dark-stainingkeratohyalin granulesContain lamellar granulesthat release lipid thatrepels water


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Stratum Lucidum Seen in thick skin onpalms & soles of feetThree to five layers of

clear, flat, dead cellsContains precursor ofkeratin


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Stratum Corneum

25 to 30 layers of flatdead cells filled with

keratin and surroundedby lipidsContinuously shedBarrier to light, heat,water, chemicals &bacteriaFriction stimulates callus

formation


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Skin GraftsNew skin cannot regenerate if stratumbasale and its stem cells are destroyedSkin graft is covering of wound with pieceof healthy skin autograft from self isograft from twin autologous skin

transplantation of patients skin grown in culture


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Dermis

Connective tissue layer composed of collagen& elastic fibers, fibroblasts, macrophages &fat cells

Contains hair follicles, glands, nerves & bloodvesselsMajor regions of dermis

papillary region reticular region


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Papillary Region

Top 20% of dermisComposed of loose CT & elastic fibersFinger like projections called dermal papillaeFunctions anchors epidermis to dermis contains capillaries that feed epidermis contains Meissners corpuscles (touch) & free

nerve endings (pain and temperature)


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Reticular Region Dense irregular connective tissue

Contains interlacing collagen and elastic fibersPacked with oil glands, sweat gland ducts, fat & hairfollicles

Provides strength, extensibility & elasticity to skin stretch marks are dermal tears from extremestretching

Epidermal ridges form in fetus as epidermis conforms

to dermal papillae fingerprints are left by sweat glands open on ridges increase grip of hand


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Skin Color Pigments (1)

Melanin produced in epidermis by melanocytes same number of melanocytes in everyone, but

differing amounts of pigment produced

results vary from yellow to tan to black color melanocytes convert tyrosine to melanin

UV in sunlight increases melanin production


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Skin Color Pigments (2)

Carotene in dermis yellow-orange pigment (precursor of vitamin A) found in stratum corneum & dermis

Hemoglobin red, oxygen-carrying pigment in blood cells if other pigments are not present, epidermis is

translucent so pinkness will be evident


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Accessory Structures ofSkin

Epidermal derivativesCells sink inward during

development to form: hair oil glands sweat glands nails


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Structure of Hair

Shaft -- visibleRoot -- below the surface

Follicle surrounds root external root sheath internal root sheath base of follicle is bulb

blood vesselsgerminal cell layer


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Hair Related Structures

A rrector pili smooth muscle in

dermis contractswith cold or fear.

forms goose bumpsas hair is pulled

verticallyHair root plexus detect hair

movement


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Hair GrowthGrowth cycle = growth stage & resting stageGrowth stage lasts for 2 to 6 years

matrix cells at base of hair root producinglength Resting stage lasts for 3 months matrix cells inactive & follicle atrophiesOld hair falls out as growth stage begins again normal hair loss is 70 to 100 hairs per day


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Hair Color

Result of melanin produced in melanocytesin hair bulb

Dark hair contains true melaninBlond and red hair contain melanin with ironand sulfur added

Graying hair is result of decline in melaninproductionWhite hair has air bubbles in the medullary

shaft


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Functions of Hair

Prevents heat lossDecreases sunburnEyelashes helpprotect eyesTouch receptors (hairroot plexus) senseslight touch


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Glands of the SkinSpecialized exocrine glands found indermisSebaceous (oil) glandsSudiferous (sweat) glandsCeruminous (wax) glands

Mammary (milk) glands


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Sebaceous (oil) glands Secretory portion in the dermisMost open onto hair shaftsSebum combination of cholesterol, proteins, fats &

salts keeps hair and skin from soft & pliable

inhibits growth of bacteria & fungi(ringworm) Acne bacterial inflammation of glands

secretions stimulated by hormones at puberty

S d if ( t)


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Sudoriferous (sweat)glands

Eccrine (sweat) glands most areas of skin secretory portion in dermis with duct to

surface regulate body temperature with perspiration

Apocrine (sweat) glands armpit and pubic region secretory portion in dermis with duct that

opens onto hair follicle

secretions more viscous


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Ceruminous glands

Modified sweat glands produce waxysecretion in ear canal

Cerumin contains secretions of oil andwax glandsHelps form barrier for entrance of foreignbodiesImpacted cerumen may reduce hearing


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Nails

Tightly packed, keratinized cellsNail body is pink due to underlyingcapillaries

Lunula appears white due to thickenedstratum basale in that areaCuticle (eponychium) is stratum corneum

Nail matrix deep to the nail root is theregion from which the nail growth occursGrowth is 1mm per week--faster in summer

& on most-used hand


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Structure of NailsTightly packed keratinizedcellsNail body visible portion pink due to

underlying capillaries free edge appears white

Nail root

buried under skin layers lunula is white due tothickened stratum basale

Eponychium (cuticle)

stratum corneum layer


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Nail Growth

Nail matrix below nail root produces growthCells transformed into tightly packed keratinized

cells1 mm per week


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Types of Skin

Thin skin covers most of body thin epidermis (.1 to .15 mm.) that lacks

stratum lucidum lacks epidermal ridges, has fewer sweat glands

and sensory receptors

Thick skin only on palms and soles thick epidermis (.6 to 4.5 mm.) with distinct

stratum lucidum & thick stratum corneum

lacks hair follicles and sebaceous glands

F ti t


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enera Functions o t eSkin

Regulation of body temperature

Protection as physical barrier Sensory receptorsExcretion and absorptionSynthesis of vitamin


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ThermoregulationReleasing of sweat onto the skin perspiration & its evaporation lowers body

temperature

Adjusting flow of blood to the body surface in moderate exercise, more blood brought to

surface helps lower temperature

with extreme exercise, blood is shunted tomuscles and body temperature rises

Shivering and constriction of surface vessels

raise internal body temperature as needed


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ProtectionPhysical, chemical and biological barrier tight cell junctions prevent bacterial invasion lipids released retard evaporation pigment protects somewhat against UV light langerhans cells alert immune system


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Cutaneous SensationsTouch, temperature, pressure, vibration,tickling and some pain sensations arisefrom the skin.


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Excretion and AbsorptionOnly a minor role is played by the skin400 mL of water evaporates from itdaily

Small amounts salt, CO2, ammonia andurea are excretedLipid soluble substances can be

absorbed through the skin


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Synthesis of Vitamin DSunlight activates a precursor to vitamin DEnzymes in the liver and kidneystransform that molecule into calcitriol(most active form of vitamin D)Necessary vitamin for absorption ofcalcium from food in the gastrointestinaltract


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Age Related Structural Changes

Collagen fibers decrease in number & stiffenElastic fibers become less elasticFibroblasts decrease in number

Langerhans cells and macrophages decrease inumber and become less-efficient phagocytesOil glands shrink and the skin becomes dry

Walls of blood vessels in dermis thicken sodecreased nutrient availability leads to thinnerskin as subcutaneous fat is lost


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PhotodamageUltraviolet light (UVA and UVB) bothdamage the skin

Acute overexposure causes sunburnDNA damage in epidermal cells can lead toskin cancerUVA produces oxygen free radicals thatdamage collagen and elastic fibers andlead to wrinkling of the skin


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Skin Cancer1 million cases diagnosed per year3 common forms of skin cancer basal cell carcinoma (rarely metastasize)

squamous cell carcinoma (may metastasize) malignant melanomas (metastasize rapidly)

most common cancer in young women

arise from melanocytes ----life threateningkey to treatment is early detection watch forchanges in symmetry, border, color and sizerisks factors include-- skin color, sun exposure,

family history, age and immunological status


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Burns

Destruction of proteins of the skin chemicals, electricity, heat

Problems that result shock due to water, plasma and plasma protein

loss

circulatory & kidney problems from loss ofplasma

bacterial infection


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Types of BurnsFirst-degree only epidermis (sunburn)

Second-degree burn destroys entire epidermis & part of dermis fluid-filled blisters separate epidermis & dermis epidermal derivatives are not damaged heals without grafting in 3 to 4 weeks & may sca

Third-degree or full-thickness destroy epidermis, dermis & epidermal derivative damaged area is numb due to loss of sensory

nerves


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Pressure Sores

Caused by constant deficiency of bloodflow to tissue

Areas affected is skin over bonyprominence in bedridden patientsPreventable with proper care


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Other Diseases

Acne Athletes Foot

DermatitisPsoriasis Vitiligo

Warts Alopecia Areata

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Seborrheic DermatitisParonychia

f h l d


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Integration of Faith, Values andLearning

Psalms 139: 14 I praise you because I am fearfully

and wonderfully made; your works arewonderful, I know that fully well.

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QUIZ

1.Give at least 2 Stratas (Layers) of theEpidermis2.What is epidermis?3.Give at least 2 types of cells found in theEpidermis.4.Differentiate epidermis from dermis5.Give two functions of hair

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6. forms goose bumps as hair is pulled vertically A. Arrector Pili B. Shaft C. Hair

7. Produces melanin pigments. A. Melanocytes B. Keratinocytes C. Merkel Cells

8. The skin is ____ square feet A.17 B. 18 C. 20

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9. Burn only in the epidermis

A. First Degree B. Second Degree C. Third Degree

10. From the bone marrow and provides immunity

A. Keratinocytes B. Melanocytes C. Langerhan Cells

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Were done!XD

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Integumentary System 343